Free‐exciton luminescence in GaSb quantum wells confined by short‐period AlSb‐GaSb superlattices

Photoluminescence and photoluminescence excitation measurements at temperatures ranging from 4 to 300 K were performed on 9.2‐nm GaSb quantum wells confined by AlSb‐GaSb short‐period superlattices. In the temperature range 4–200 K the photoluminescence from the high‐quality molecular beam epitaxially grown samples is dominated by free‐exciton emission. This assignment is confirmed by photoluminescence excitation spectroscopy which reveals an energy separation of 11.5 meV between n=1 heavy‐hole and n=1 light‐hole free excitons for the 9.2‐nm wells. At low temperatures the photoluminescence line is shifted by only 7.5 meV to low energy from the heavy‐hole excitonic peak observed in the excitation spectrum. This small value of the Stokes shift indicates the absence of impurity‐related trapping of excitons.